1. Field of the Invention
The present invention relates to electronic devices for sensing, capturing, and signal processing, and more particularly to an image sensor fabricated by a standard complementary metal oxide semiconductor (CMOS) process.
A claim of priority is made to Korean Patent Application No. 2002-0049783, filed Aug. 22, 2002, the contents of which are incorporated herein by reference.
2. Description of the Related Art
CMOS image arrays make it possible to handle high quality images with a video camera that may be variously used in camcorder apparatuses, scanners for fax machines, and portable apparatuses for video conference or professional TV broadcasting, for example.
The presence of multimedia communication has resulted in an increasing demand for low-cost solid state image sensors for use in computers and communication equipment in order to realize practical videotelephones. Image input devices have become key elements of teleconference and multimedia applications. In recent years, CMOS image sensors have become attractive as a candidate for image input devices. Also, CMOS image sensors may be applied to robotics, machine vision, security surveillance, automobile, and personal identification (ID) systems that use fingerprint analysis and retina scanning.
In a CMOS image sensor, a signal processor and an imager can be integrated on the same chip. Therefore, a smart design can be achieved and the CMOS image sensor can be implemented as a single-chip image capture system. Since a CMOS imager can be fabricated in CMOS process lines without modification of the process lines, such fabrication is low-cost as compared to fabrication costs of conventional charge coupled devices (CCD).
Recently, the use of portable electronic apparatuses has been increasing. Because portable electronic apparatuses receive power from a battery, electronic apparatus developers have focused efforts on developing low-power consumption portable electronic apparatuses. Accordingly, there is a need for a low-power consumption image sensor for use in portable electronic apparatuses which require image capture.
It is well known that light is successively varied analog data. The analog data must be converted into digital data so as to be processed into a discrete signal. A CMOS image apparatus employs an analog-to-digital converter for detecting light as an analog signal, in order to convert the analog signal into digital data. By saving power consumed by the analog-to-digital converter, power consumed by the CMOS image apparatus as a whole may be saved.